According to the state of the art, automatic transmission, especially for motor vehicles, include planetary sets, which are shifted by way of friction or shifting elements, such as clutches and brakes, and are generally connected to a starting element which is subject to slip action and is optionally equipped with a bypass clutch, such as a hydrodynamic torque converter or a fluid clutch.
Such a transmission is disclosed in EP 0 434 525 A1. It essentially comprises an input shaft and an output shaft, which are arranged parallel to each other; a double planetary gear set arranged concentric with the output shaft and five shifting elements in the form of three clutches and two brakes, the selective lockup of which determines, in pairs, the various gear ratios between the input shaft and the output shaft. The transmission comprises a front-mounted gear set and two power paths so that six forward gears can be achieved by selectively engaging the five shifting elements in pairs.
With the first power path, two clutches are required for the transmission of torque from the front-mounted gear set to two elements of the double planetary gear set. These are arranged in the direction of power flow essentially behind the front-mounted gear set in the direction of the double planetary gear set. With the second power path, another clutch is provided, which connects it detachably to another element of the double planetary gear set. The clutches are arranged such that the inside multi-disk carrier forms the output.
Furthermore, a compact multi-speed transmission of planetary construction, especially for a motor vehicle, is known from U.S. Pat. No. 6,139,463, which comprises two planetary gear sets and one front-mounted gear set as well as three clutches and two brakes. In this familiar multi-speed transmission, two clutches C-1 and C-3 are provided in a first power path for transmitting torque from the front-mounted gear set to the two planetary gear sets. Here the outside multi-disk carrier and/or the cylinder or piston and pressure compensating side of the clutch C-3 is connected to a first brake B-1. Additionally, the inside multi-disk carrier of the third clutch C-3 is connected to the cylinder or piston and pressure compensating side of the first clutch C-1, wherein the inside multi-disk carrier of the first clutch C-1 is arranged on the output side and connected to a sun gear of the third planetary gear set.
Moreover, a multi-speed transmission is known from DE 199 49 507 A1 in which two non-shiftable input-side gear sets are provided, which generate two rotational speeds on the output side which, apart from the rotational speed of the input shaft, optionally can be shifted to a shiftable double planetary gear set acting upon the output shaft by selectively engaging the shifting elements that are used in such a way that for shifting from gear to the next higher or lower gear of the two just actuated shifting elements, only one shifting element has to be activated or deactivated.
From DE 199 12 480 A1, an automatically shiftable motor vehicle transmission is known comprising three single-spider planetary sets as well as three brakes and two clutches for shifting six forward gears and one reverse gear and comprising one input and one output shaft. The automatically shiftable motor vehicle transmission is designed such that the input shaft is connected directly to the sun gear of the second planetary set and that the input shaft can be connected to the sun gear of the first planetary set via the first clutch and/or to the spider of the first planetary set via the second clutch. Additionally or alternatively, the sun gear of the first planetary set can be connected to the housing of the transmission via the first brake and/or the spider of the first planetary set to the housing via the second brake and/or the sun gear of the third planetary set to the housing via the third brake.
Furthermore, a multi-speed automatic transmission is known from DE 102 13 820 A1, comprising a first input path T1 of a first gear ratio; an input path T2, which has a larger gear ratio than input path T1; a planetary gear set with four elements, wherein the four elements are a first element, a second element, a third element and a fourth element in the sequence of the elements in a speed diagram; a clutch C-2, which transmits a rotation of the input path T2 to the first element S3; a clutch C-1, which transmits the rotation of the input path T2 to the fourth element S2; a clutch C-4, which transmits a rotation from the input path T1 to the first element; a clutch C-3, which transmits the rotation from the input path T1 to the second element C3; a brake B-1, which establishes the engagement of the fourth element; a brake B-2, which establishes the engagement of the second element, and an output element, which is coupled to the third element R3.
A multi-speed transmission is described within the framework of DE 101 15 983 A1 by the Applicant comprising an input shaft, which is connected to a front-mounted set; an output shaft, which is connected to a rear-mounted set, and with no more than seven shifting elements, whose selective shifting allows at least seven forward gears to be shifted without a range shift. The front-mounted set is formed by a front-mounted planetary gear set or no more than two non-shiftable front-mounted planetary gear sets that are coupled to the first front-mounted planetary gear set, wherein the rear-mounted set is designed as a two-spider, four-shaft gear with two shiftable, rear-mounted planetary gear sets and comprises four free shafts. The first free shaft of two-spider, four-shaft gear is connected to the first shifting element; the second free shaft to the second and third shifting elements; the third free shaft to the fourth and fifth shifting elements, and the fourth free shaft is connected to the output shaft. For a multi-speed transmission with a total of six shifting elements, according to the invention it is suggested to connect the third free shaft or the first free shaft of the rear-mounted set additionally to a sixth shifting element. For a multi-speed transmission with a total of seven shifting elements according to the invention it is suggested to connect the third free shaft additionally to a sixth shifting element D′ and the first free shaft additionally to a seventh shifting element.
Furthermore, within the framework of DE 10115 987 by the Applicant, a multi-speed transmission with at least seven gears is described. This transmission consists, apart from the input shaft and the output shaft, also of a non-shiftable, front-mounted gear set and a shiftable rear-mounted gear set in the form of a two-spider, four-shaft transmission. The front-mounted gear set consists of a first planetary gear set, which (apart from the input rotational speed of the input shaft) offers a second rotational speed, which can be optionally actuated on the rear-mounted gear set. The rear-mounted gear set consists of two shiftable, planetary gear sets, which can shift at least seven gears using the six shifting elements, thus forming two power paths. In doing so, during each shifting operation beneficially always range shifts are avoided. A 9-gear multi-speed transmission is furthermore known from DE 29 36 969; it comprises eight shifting elements and four gear sets.
Automatically shiftable motor vehicle transmissions of planetary construction have, in general, been described numerous times in the prior art and are subject to permanent development and improvement. These transmissions reportedly have a sufficient number of forward gears as well as a reverse gear and a well-suited gear ratio for motor vehicles with a high overall gear ratio spread as well as favorable progressive ratios. Furthermore, they are intended to enable a high starting gear ratio in the forward direction and contain a direct gear, and they are supposed to be suited for use both in passenger vehicles and commercial vehicles. Moreover, these transmissions reportedly require little construction expenditure. In particular, they require a small number of shifting elements, and reportedly avoid double-shifting during sequential shifting so that only one shifting element is changed when shifting in defined gear groups.
It is the object of the present invention to suggest a multi-speed transmission of the above-described kind, in which the construction effort is optimized and, additionally, the efficiency in the main travel gears is improved in terms of drag and gearing losses. Furthermore, with the multi-speed transmission of the invention, low torque is intended to act upon the shifting elements and planetary sets and also the rotational speeds of the shafts, shifting elements and planetary sets are supposed to be kept as low as possible. Furthermore the number of gears as well as the spread of gear ratios is supposed to be increased so that beneficially seven forward gears and at least one reverse gear can be implemented. Moreover the transmission of the invention is supposed to be suited for any vehicle design, especially for a front-transverse arrangement.
This object is achieved pursuant to the invention by the features of patent claim 1. Further benefits and beneficial embodiments are revealed in the dependent claims.